Electrical measuring instrument.



F. W. MORRIS. ELECTRICAL MEASURING INSTRUMENT.

AYPLIOATION YLED DEC.24.1012

Patented Dec 8, 1914.

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ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED DEC. 24. 1912. 1,120,211 Patented Dec.8,1914.

2 SHEETS SHEET Z.

UNITED STATES PATENT OFFICE.

FREIJERICK W. MQRRRK. if BROGKLYN, N'E'N YORK. ASSTGIWJR T0 THOMAS E. MURRAY, GE NEVJ YClHK, N. Y.

ELECTRICAEZ MEASUEIN G INSTRUMENT.

Application filed December 24, 3.912.

To all 'u'lmm it may concern Be it knoivn that I, FREDERICK W. Mm RIS, a citizen of the United States. residing at Brooklyn, in the county of Kings and State of New York, have invented a certain new and useful Improvement in Electrical Measuring Instruments. of which the following is a specification.

The invention is an electrical measuring instrument, wherein the current is measured bv the mutual reaction of two fields, one of said fields being constant and produced around a movable member, and the other of said fields being produced by induction from a conductor separate from the instrument. and conveying the current to be measured; the said second field hence being variable correspondingly to said current. The second field is preferably concentrated by a body of magnetic material preferably of high pern'ieability, wherein the flux is gen erated by the current to be measured. in which body there may be an air-gap wherein the movable member may be placed. The displacement of said movable member resiliently opposed so that said member finally takes a. position of balance. and the extent of its travel in passing to said position then measures the inducing current aforesaid.

In the accompanying drawings-Figure 1 is a front elevation of my electrical measuring instrument, Fig. 2 is a side elevation, Fig. 3 is a rear elevation, Fig. 4 is a detail view in perspective, showing the coil and body of magnetic material in inductive proximity thereto. and Fig. 5 is an electrical diagram showing the circuit in the instrumcnt.

Similar letters and nimib rs of refer-crave indicate like parts.

Referring first to Fig. 5. the coil A is: pivoted in inductive prox mity to a body l? of magnetic material. The coil terminals are connected to the rebate springs J, K which oppose the angular displacement of the coil on its pivots. E is a voltaic cell of any suitable type giving a substantially constant current. One terminal of said cell is connected to voluie spring J, and the other through a variable resis ance F and snitch G to the volute spring 13:, so that the circuit proceeds from cell E. to spring J through the coil A, to spring K. to variable reslstanco F, and so back to cell E.

In using the nstrument. the trai il of Specification of Letters Patent.

Patented Dec. 8, 1914.

Serial No. 733.442.

magnetic material is placed in inductive proximity to the conductor conveying the current to be measured, which conductor is separate from the instrument. In Fig. 5, said conductor, indicated at H, is shown disposed between the arms of the body B which is in loop form. The coil A being located in an air-gap between the extremities of body B, is in. 1: variable magnetic field, and is caused to turn on its pivot by reason of the mutual reaction oil said field with the field due to the current traversing said coil. Inasmuch as the current in the coil is constant, or substantially so, the angular displacement of the coil against the resilient opposition of springs J, K Will de pend upon variations in strength of the field in which the coil is pivoted. And as this in turn depends upon the current traversing the conductor H, it follows that the extent of angular displacement of the coil will measure the strength of said current.

Referring now to the siiiecific construction of the instrument here illustrating my invention. 1. is the inelosing case. having an opening. through which the ind needle 2 and scale can be seen. (lo. the r side of the case are secured two brackets and i. The upper bracket 3 carries the horizontally disposed constant cell E. one terminal of which is formed by its cvlindrical metal envelop. The other terminal. 5, is centrally disposed at one end. of the cell. On the under side (If bracket 3 is supported the cylindrical metal core ll. flctween the brackets 3 and 4 are fastened the concave ll. llf. The core ll is disposed between and in the nraxitic of said blocks.

i f betwccnsaid ii i5. end to the blori: Fr 2: U-

hop rated i13 ll of magnetic material. .lhe other end of said bar is releasably secured bv a removable screw (5 to the block B The core B, blocks B, B and 100 B l3 and s pivotedi n ha rs 8 extending be- 110 wuril arms 9, 10, by means of which the wsi icncy of said springs and hence the opo ition oilered by them to the angular displacenwnt of the coil may be adjusted, all as in the Weston instrument aforesaid. The arm 1'0, Pig. 1, is connected by wire 11 to the i1" spring contact 12 on post 13. Another act 14, secured to a plate 15 of material fastened to the side of vac. connected by wire 16 to the movable member 17 of the variable resistance F, ported on a shoulder formed on (ii the ase. The fixed coil 18 of tar e is connected by wire 19 to teral a oi' cell 16, Fig. 3. The arm 9 is con- .ed by wire 26 to binding post 21, which wannectcd by wire 22 to the tubular me-- Luilif? \znvclo of cell E. The function of the variable resistance in instruments of this type is already well understood. The func tion of the spring switch G formed by contacts if and l t is to keep the circuit in the Mvunient norn'ially open, and thus avoid t liaustion of the cell. The index needle 2 is secured to coil A. and extends over the scale which. is marked in suitable units of measuren'ient, such as volts.

The laminated bar B is flexible, and when the screw 6 is Withdrawn from the block B n; end of said bar, secured by said screw, may be separated from said block, as indi .'-.-d in. dotted lines, Fig. 1, so as to allow w conduiictor ll, shown in Fig. 1 as a cable and carry ng the current to be measured, to or placed within the loop of said bar. The end of the bar is then re-secured to block B The varying current on conductor H a flu); in bar B and blocks B, B", iorming part of the same magnetic struc ture, whereby a strong variable field is produced in the annular space between blocks B B The constant current from cell I trmersing coil A produces a constant field which, coacting with the variable field, ca uses the coil A to be angularly displaced to a point where the resilient action of the two fields is balanced by the resiliency of the springs J, K, and this displacement, as indicated by the index needle 2, is read in terms of the units marked on the scale.

It is to be noted that this instrument has no exterior terminals connected to it, since it obtains its variable field solely by induction. It is, therefore, especially adapted to the measurement of current on the cables and other leads of power, electric lighting ow l lac installations, inasmuch as it can be a -d to a lead at any exposed point'along the length thereof, without requiring any opening of the circuit.

The bar 8 should be of high magnetic permeability. it is here laminated to reduce residual magnetism. Any remaining in it is compensated for by suitable scale corrections.

I claim:

1. An electrical measuring instrument, comprising a movable member, means for resiliently opposing the movement of said member, and means for controlling the movement of the movable. member adapted to be energized by a flux surrounding a conductor separate from the instrument, the current upon which conductor is to be measured.

2. An electrical measuring instrument, comprising a movable member, means for resiliently opposing the movement of said member, means for controlling the move ment of the movable member adapted to be energized by a flux surrounding a conductor separate from the instrument, the current upon which conductor is to be measured, and means for indicating the displacement of said movable member.

3. An electrical measuring instrument, comprising means for producing a constant field, means adapted to be energized by a flux surrounding a conductor separate from the instrument, the current upon which conductor is to be measured to produce a second field, and a movable member disposed in both fields and adapted to be displaced by their mutual reaction.

4. An electrical measuring instrument, comprising a movable member, means for energizing said member to produce a constant field, means for resiliently opposing the movement of said member, a fixed mem ber disposed in said field and adapted to be energized by a flux surrounding a conductor separate from the instrument, the current upon which conductor is to be measured, to produce a second field, and means for indicating the displacement of said movable member due to the mutual reaction of said fields.

5. An electrical measuring instrument, comprising a coil rotary on a diametral axis, means for resiliently opposing the movement'of said coil, a current generator in circuit with said coil, and a body of magnetic material in inductive proximity to said coil and adapted to be energized by a flux surrounding a conductor separate from the instrument, the current upon which conductor is to be measured.

6. An electrical measuring instrument, comprising a body of magnetic material in loop form adapted to be energized by a flux surrounding a conductor separate from the instrument, the current upon which conductor is to be measured, a coil rotary on a diame'tral axis interposed between the arms of said loop, and a current generator in circuit with said coil.

7. An electrical measuring instrument,

comprising '5, body of magnetic material adapted to be energized by a flux surrounding a conductor'separate from the instrument, the current upon which conductor is to be measured, and having an air gap, :1 pivoted coil in said gap, means for resiliently opposing the angular displacement of said coil, and a current generator in circuit with said coil.

8. An electrical measurin instrument,

' comprising a support, two b ocks of magnetic material thereon having concavities in their opposing faces, a, 'U-shaped bar of magnetic material secured at one of its ends to one of said blocks and having its other end releasabl connected to the other of said blocks anda apted to be energized by a flux surrounding a conductor separate from the instrument, the current upon which con- (luctor is to be measured, a coil pivoted in said concavi'ties, means for resiliently opposing the movement of said coil, and a current generator in circuit with said coil.

9- An electric measuring instrument, comprising a body of magnetic material, a moving coil in inductive proximity thereto, and means for placing said body in inductive relation with a conductor separate from the instrument so as to measure the current passing through said conductor. 

